Measurement of the t dependence in exclusive photoproduction of mesons at HERA

The exclusive photoproduction reaction γp→Υ{hooked} (1S)p has been studied with the ZEUS detector in ep collisions at HERA using an integrated luminosity of 468 pb -1. The measurement covers the kinematic range 60<W<220 GeV and Q 2<1 GeV 2, where W is the photon-proton centre-of-mass energy and Q 2 is the photon virtuality. The exponential slope, b, of the t dependence of the cross section, where t is the squared four-momentum transfer at the proton vertex, has been measured, yielding b=4.3-1.3+2.0(stat.)-0.6+0.5(syst.) GeV-2. This constitutes the first measurement of the t dependence of the γp→Υ{hooked} (1S)p cross section.